It is not yet possible in case of the pressure-supported or pressure-controlled respiration (also known as a ventilation) of patients to automatically adapt the changes in the respiration pressure over time as well as the duration of the inspiration breathing stroke to the individual breathing mechanics of the patient and especially to the patient's lung diseases or limitations.
Such an adaptation to the patient's clinical picture would, however, be desirable, because the breathing or lung mechanics of, e.g., a patient with Chronic Obstructive Pulmonary Disease (COPD) differs from that of a patient with Acute Respiratory Distress Syndrome (ARDS), which also affects the optimal mechanical respiration. For example, the compliance of a patient with COPD is comparatively high, whereas patients with ARDS have a comparatively low compliance.
It is advantageous for COPD patients to be respirated with an initially high airway pressure and with a comparatively low pressure at a later stage of the inspiration to overcome resistive resistances. These patients require a time that is above average for the expiration. To guarantee sufficient expiration during passive breathing out, the duration of inspiration is therefore selected to be usually short and the inspiration pressure to be high (see FIGS. 1 and 2). If excessively long inspiration times are selected, overinflation of the lungs may, however, occur, especially in case of respiration with pressure support and/or a flow-based cycle-off criterion selected as an excessively insensitive criterion. Moreover, asynchronous patient activity, which counteracts the relaxation of the muscles and facilitates the build-up of a PEEP, is often facilitated. This is disadvantageous for the patient.
Contrary to this, ARDS patients must be respirated cautiously with high pressures in order to achieve a sufficient gas exchange. The necessary pressure is usually increased gradually to the maximum inspiration pressure. By contrast, comparatively little time is needed for the expiration, because the strong elastic resetting forces help expel the gas volume breathed in rapidly. Short expiration times are therefore regularly selected, also increased to prevent recruited lung areas from collapsing by achieving an intended intrinsic PEEP. However, the respiration of ARDS patients leads, especially when the flow-based cycle-off criterion common in case of pressure support is used, to very short inspiration times and to a patient activity that is asynchronous in relation to the respiration pattern, as this can be seen in FIG. 3.